The smoking of tobacco has been widespread throughout the world for many years. However, it has recently been shown that tobacco smoke is harmful not only to habitual smokers, but also to nonsmokers. Thus, there have more recently been considerable concern about the health hazards caused by tobacco smoke.
Tobacco smoke contains thousands of components of various kinds, many of which are harmful to the human body and some of which are shown to be carcinogenic and/or mutagenic.
In order to remove and reduce these toxic components from tobacco smoke, there have been proposed filters consisting of cellulose acetate fiber and those containing activated carbon. These filters reduce harmful components of tobacco smoke to a certain extent, but the efficiency is still unsatisfactory. For example, these filters do not selectively adsorb ionic or polar components of tobacco smoke, many of which are highly harmful.
Activated carbon is frequently used in the form of fine grains and in combination with cellulose acetate fiber. These fine grains of activated carbon readily aggregate with each other due to tar formed during smoking and rapidly lose their surface activity. Moreover, these grains are difficult to be mixed uniformly with cellulose acetate fiber and readily separate and fall off from the fiber. Therefore, it is difficult to handle grains in filter production and to disperse grains uniformly in the filter. Accordingly, ideal contact of smoke with these grains in conventional tobacco filters cannot be achieved. Similar problems arise even when ion exchange resin grains are used in place of activated carbon grains. Thus, these granular substances cannot be made effective enough to reduce the levels of toxic components in tobacco smoke.
It is difficult to prepare a sheet such as a paper for other filter uses from the granular substances. Though it has been proposed to use a layer of powdered ion exchange resin as pre-coat filter in a pure water producing process, such filters are very fragile, break too easily, and inevitably cause a large pressure drop during filtration.